The intracellular cAMP and Ca2+ levels in opsin-expressing HEK293S cells were measured using the GloSensor cAMP assay and the aequorin assay, respectively, as described previously (22 (link), 26 (link), 69 (link), 70 (link)). The pGloSensor-22F cAMP plasmid (Promega) was used for the GloSensor cAMP assay. The wild-type aequorin obtained by introducing two reverse mutations into the plasmid [pcDNA3.1+/mit-2mutAEQ] (Addgene #45539) (71 (link)) was used for the aequorin assay. A broadband green LED light and narrow-band violet (410 nm) and blue (430 nm) LED lights were applied for 5 s in the GloSensor cAMP assay and for 1 s in the aequorin assay as light stimuli.